Visual Search in Air Combat

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AD-A241 347

VISUAL SEARCH IN

AIR COMBAT

S. Schallhorn, K. Daill, W.B. Cushman,

R. Unterreiner, and A. Morris

OTICS%LECTEOCT 0 a1991

91 1 0

Naa"Aerospace Medical Research LaboratoryNaval Air Station

Pensacola, Florida 32508-5700

Approved for public release; distribution unlimited.



This report has been reviewed and is approved for publication.

JAM B Y , CAPT, MSC, USN RUSSELL M. TAYLOR, /I, APT, USNCommanding Officer Commanding Officer

Naval Aerospace Medical Navy Fighter Weapons School

Research Laboratory

NOTICES

This report was submitted jointly by personnel of the Naval Aerospace Medical

Research Laboratory, Pensacola, Florida, under work unit number 63706N

M0096.002 and the Navy Fighter Weapons School, Miramar, California.

The views expressed in this article are those of the authors and do notreflect the official policy or position of the Department of the Navy,

Department of Defense, nor the U.S. Government.

Reproduction in whole or in part is permitted fo r any purpose of the United

States Government.



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Visual Search in Air Combat

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6. AUTHOR(S) M0096.002-7050S. Schallhorn*, K. Daill, W.B. Cushman**, R. Unttrreiner, DN 249510and A. Morris

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Naval Air Station NAMRL Monogrph 11Pensacola, Fl. 32508-5700

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11 . SUPPLEMENTARY NOTES -S.•chaIlnorn's contribution to this project was made duringhis residency at the Ophthalmology Department, Naval Hospital, San Diego. **/,portion of W.B. Cushman's contribution to this project was made during an Office oNaval Technology (ONT) Postdoctoral Fellowship appointment at NAMRL.

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13. AJSTRACT (Maximum 200 words)

Visual search and detection remains as the most important sensor for the aircrew otactical aircraft. Detection of airborne targets is directly related to the Combateffectiveness of the fighter/strike mission. This monograph, the product of acoordinated effort between the Naval Aerospace Medical Research Laboratory (NPMRL)and the Navy Fighter Weapons School (NFWS), TopGun, covers the basics required tooptimize visual search in combat. The document is intended as an instructional aidto aircrew of tactical aircraft, especially those involved in aerial combat. Thefollowing four topics are discussed in this monograph: (a) sensors: means ofdetection; (b) equipment: obstructions to vision; (c) detection: the eye as asensor; and (d) search: using the sensor.

14. SUBJECT TERMS 18NUMBER OF PA-,E

visual search vision air combat tactics 16 . PRICE8CODE

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ABSTRACT

Visual search and detection remains as the most important sensor for

aircrew of tactical aircraft. Detection of airborne targets is directly

related to the combat effectiveness of the fighter/strike mission. This

monograph, the product of a ccordinated effort between the Naval Aerospace

Medical Research Laboratory (NAMRL) and the Navy Fighter Weapons School

(NFWS), TopGun, covers the basics required to optimize visual search incombat. The document is intended as an instructional aid to aircrew of

tactical aircraft, especially those involved in aerial combat. The following

four topics are discussed in the monograph: (a) sensors: means of detection;

(b) equipment: obstructions to vision; (c) detection: the eye as a sensor;

and (d) search: using the sensor.

Accesion For

N!S CRA&tDTIC TAB ]

Unano,,: -;ed .

Ji~strfcit:o; I

y. . ...........By ...... ... . .... .. . ....... .. . .... ...

Di hAib.:-A.

Avaii~lb iy . ,'Dist Sp, ,i

iii



INTRODUCTION

The eye remains as the most important sensor fo r aircrew of tactical

aircraft. Its importance to visual search and detection has not changed since

the early days of air combat. A fighter who loses sight of or never detects

the enemy can quickly succumb to hostile fire. Regrcttably, this lesson has

been learned too many times. Simply put, with inadequate visual search intoday's multithreat environment, the chance of survival is greatly diminished.

As technology advances, we will rely more and more on passive sensors andvisual search. This will be the case in a full-stealth environment. The

radar cross section of an aircraft will be a fraction of what it is in today'sfighters. Detection using conventional radar will be difficult and likely tooccur at a greatly reduced range. The aircraft that illuminates first will bequickly detected and targeted by accurate, state-of-the-art passive sensors.

The importance of visual detection has not diminished with technological

advances.

This monograph will concentrate on the effective use of visual search by

aircrew of fighter/strike aircraft. It reviews the basic principles ofdetection in the high-workload environment of air combat. It results from acoordinated effort between the Naval Aerospace Medical Research Laboratory

(NAMRL) and the Navy "'ighter Weapons School (NFWS), also known as TopGun,While the detection ol airborne targets is directly related to the combat

effectiveness of the fVghter/strike mission, aircrew of all tactical aircraft-

will benefit from the information presented herein:

a. Sensors: means of detection.

b. E4uipment: obstructions to vision.

c. Detection: the eye as a sensor.

d. Search: using the sensor.

SENSORS: MEANS OF DETECTION

Four categories of sensors are available to aircrew fo r the detection of

aerial targets: onboard tactical radar, onboard threat warning receivers,

radio communications (wingman, GCI, etc.), and aircrew visual search. Th einherent advantages and disadvantages of each are briefly reviewed.

Onboard Radar

The onboard radar system has the capability of searching, Interrogating,and tracking aircraft within it s scar volume, It can do this at ranges fat

greater than that of visual detection. With a radar lock, the head-up display

can superpose a bix/diamond over the targeted airclaft to assist visual

acquisition. However, this 'single target track' mode ties up the radar'ssearch capability and leaves it with very limited capability to search anddetect aircraft within 5 miles of the fighter. The pilot has some capabilityto achieve radar assisted visual detection when the radar is operating in itssearch mode. This rquires a knowledge of angular reference points around the

cockpit and an effective search technique. The radar system has no capability

to detect an incoming air-to-air missile.



The most important inherent disadvantage of the onboard radar becomes

apparent when one considers its maximunm search area. Typically, this wouid

approximate a 60-degree cone. This represents less than 10% of the total

search area around the aircraft. To put this in another light, 90% of the sky

remains untouched by that multimillion-dollar machine in the front of the

aircraft (see Fig. 1).

Figure 1. The search area of tactical airborne radar

represents less than 10% of the total search

field around an aircraft.

A television camera system, such as the one in F-14 aircraft, gives the

aircrew an additional sensor. It can facilitate a 'beyond visual range' shot

when positive visual identification is required. Without this equipment, a

visual identification often requires,the two aircraft to approach within 1

mile or less. This television syster' cannot be used to perform free search

because of its narrow 15-degree gimbal l

Onboard Threat Warning Receiver

Threat warning receivers were designed primarily to warn against ground-

based radar threats. They have limited air-to-air application. The technol-

ogy is available fo r more advanced airborne threat interrogation, but this has

no t yet been incorporated into fleet aircraft. The best that current warning

receivers can do in the air-to-air environment is to alert the aircrew of a

potential threat within a given sector. Even tLen, the aircrew must still

detect aircraft visually to employ effective countertactics.

Radio Communications (Wingman, GCI. Etc,)

All fighter/strike aircrew recognize the value of a wingman fo r thteat

detection and mutual support. Even though the wingman will be using the same

sensors as the pilot, search effectiveness is multiplied by splitting respon-

sibilities; more will be said about this later. An incoming missile is far

easier to spot when the plume is viewed fo r the wingman to report the siting

2



from the side (by the wingman) than when seen head-on; howo'ver, radio communi-

cation is essential.

Similarly, another aid to detection, which also relies on radio communi-

catiors, is the ground/airborne radar control. These radar systems have the

capability of scanning the fighter's entire hemisphere. This global view can

be of great benefit bu t is dependent upon several criteria.The radar needs

to be fully operational, and it must illuminate the fighters. The controller

must have the situational awareness to give the fighters what they need when

they need it. Planned emissions blackout or mutual communications jamming

would eliminate the advantages of this means of detection.

Aircrew Visual Search

The use of the human eye to detect target aircraft or missile threats is

termed visual search. Vision has its limitations, such as relatively short

range and poor detection at night or in the clouds, but, as a system, it is

almost always functional and ready fo r use. Vision is the only positive means

to check the airspace around the fighter's aircraft. Visual search and

detection is & complex procedure that requires continuous training and must be

thoroughly integrated into the fighter pilot's game plan. Fighters must

always strive fo r total awareness of the space around their aircraft . This is

primarily accomplished by visual search.

EQUIPMENT: OBSTRUCTIONS TO VISION

Effective visual search requires a clear, unobstructed view of the

target. A properly fitting helmet is required that will no t restrict vision

or slide around under g-forces. The mask cord should be secured so that it

will not snag while the pilot twists his head around during visual search.

The decision to use a dark visor or sunglasses is a personal one. Either

one can reduce the abilit,, to detect a target at maximum range (1). Visual

acuity improves with an increase in luminance up to about 1000 candelas per

meter squared, then falls off. This translates to optimum acuity at a light

level equivalent to daylight outdoors on a cloudy day. Standard-issue aviator

sunglasses and visors (with 12% transmission) will reduce bright sunlight to

about this level but will reduce acuity if the sky is no t bright enough. As a

rule of thumb, if the light is so bright that ic causes discomfort, you should

probably be using the sunglasses or visor. If there is no discomfort without

these filters, don't use them.

Clear canopies and windscreens are vitally important. A dirty or

scratchy canopy can greatly reduce the relative contrast of the target and,

hence, detection ranges. Avoidable problems include paint overspray and

scratches from improper polishing or cleaning. Protect the canopy like a

fine pair of glasses.

The largest obstruction to vision is the fighter aircraft. It occupies

almost half of the visual hemisphere. In addition to looking around the

canopy bow, the fighter needs to move his aircraft to see below and aft.

Drop-ing a wing, first one direction then the other, will fill in these gaps

in the search field.

3



The fighter should continually practice putting his "head on a swivel."

This will prevent him from being his owx, worst obstruction to vision. With a

wingman, perform a simple tail chase as time and fuel dictate. With the

harness unlocked, turn around as much as the cockpit will allow and practice

looking ever the other shoulder. This will also demonstrate how to adjust

the seat fo r the best rear vision. In a similar fashion, check all equipment

fo r optimum visual performance. Fly with the lap straps tightly fastened.

Loose lap belts have been implicated in several spin accidents.

DETECTION: THE EYE AS A SENSOR

Fixations

When no t tracking a moving target, voluntary eye movements are made up of

a series of discrete fixations called "saccades." You can demonstrate this

fo r yourself. Get a friend to track your moving finger and observe his eyes.

You will see a smooth movement that corresponds to the movement of your

finger. Now, hold still and ask him to make the same eye movements withoutthe moving target. He may think that he is doing it, but if you observe

closely, you will see that his eyes make a series of discrete "jumps." It is

impossible fo r normal subjects to make voluntary smooth eye movements withouta moving target except under very contrived laboratory conditions (subjects

can make voluntary smooth eye movements with "stabilized" images or with an

after-image in the dark). This is important because during saccadic eye

movement, visual perception is minimal (2). Technically, this phenomenon is

called "saccadic suppression." You could scan a volume of sky and think that

you have eliminated the possibility of danger from that sector and be quite

wrong! Think of the eyes as moving from one fixation point to another. In

this respecc, visual search is considerably different from radar search. The

important concept is that between each fixatior i.oint acuity falls off

sharply, making it possible fo r targets to go undetected with improper search

tecnniques. This will become clearer as you read on.

Generally, the eye can make about three fixations per second (3). Thiscovers the time to perceive a target and move to another point. Eye movement

is much faster than head movement.

Focus

Clear, sharp focus is very important in visual detection. The eye is

focused by muscles that control the curvature of the lens. Without visual

stimulus, these muscles tend to relax. This would be the case when shifting

gaze from inside the cockpit co a featureless blue sky or cloud background.

It can result in a focus less than 10 feet away (4). Objects at infinity (foi

practical purposes optical infinity is anything over 20 feet) will not be

correctly imaged on the retina--they will be blurred. The contrast between

the object and the background will be reduced as the light from the target is

distributed over a larger area. Target contrast, in turn, is the prime factor

determining detection range. Out-of-focus eyes can effectively negate the

ability to see any aircraft, even your wingman. This problem is easily

corrected by first directing the eyes to a distinct, distant object such as a

sharp horizon or some cloud or land feature. This will set the correct focus

of the lens fo r subsequent, effective visual search (5).

4



Perjpheral Vision

Central vision is used when lookling directly at an object. Peripheral

vision is measured in degrees off of this central point. Visual acuity is thce

abtlity to distinguish detail in perceived objects. Acuity declines th e

farthe. a target is from the central visual axis (6). The relationship

between acuity and central and peripheral vision can be displayed as the

visual detection lobe, shown in Fig. 2, which represents the range where

visual perception of the target can occur (7). It reflects central and

peripheral visual detection capability during one fixation under a specific

se t of conditions. Think of the lobe as being attached to the eye and moving

with it during subsequent fixations. It is plotted as a function of probabil-

ity of detection versus angles off the central visual axis. If che target is

inside the lobe, the probability of perceiving it is higher. Chances are that

the target will not be seen if it lies well outside of the lobe. Actually,

the change in acuity is gradual, and the lobe just represents a given prob-

ability of detection. It is a useful mathematical expresslon to analyze

search.

B

4VISUAL AXIS

A

---- RANGE NM--0

Figure 2. The visual detection lobe.

In Fig. 2, consider three locations (A,B,C) of the same type aircraft.

Target A can be seen because. it lies within the lobe. In fact, it is being

directly viewed by central vision. Target B, outside the detection1 lobe, is

at the same range as A. Because it is no t being directly viewed and acuity

declines rapidly off axis, it cannot be perceived. Target C is the same degree

off axis as B, but because it Is closer (and hence appears larger), it can be

detected in peripheral vision. Once perceived peripherally, the next fixation

is likely to be placed right on it. Then, target B will become obvious as it

will be well inside of maximum detection range fo r central vision. Because

central vision has such a narrow field of view (less than 2 degrees),

perirheral vision is the key to rapid detection, bu t realize that peripheral

vision does no t have the detection range of central vision.

Optimizing Detection

To optimize detection, you should examine f.,ctors that affect the size of

the detection lobe. The main objective is to make threat aircraft easier to

see while keeping the fighters hidden.

5



Target size determines the deLection lobe size by increasing or decreas-

ing the visual image size and, hence, the detection range. A head-on aircraft

is much harder to see than one with a side or belly view because the i

& is smaller. This principle is demonstrated in Fig. 3. Under a vory

specific set of conditions, this graph estimates the maximum (central acuity)

visual detection ranges fo r several aircraft with extremes of target aspect

(front, side, and belly views). This is based on a comprehensive study offighter pilot vision conducted by the Naval Aerospace Medical Research

Laboratory, NAMRL (8).

14-

13 -

0) 2

E 11

.2

0 I-

. 10-

_J4--.IE VE

29-

S8w( 7

Z ______BELLY VIEW< MI MMG F-1#

(L 21 23 25

PR OJECTEDAREA--RONT VIEWwMIG MIG F"- 421

2 3M1G P

X 2b

W 0

- j : " I I I I - I I I I I I0 200 400 600 800 1000 1200 1400

PROJECTED AREA (square feet)

Figure 3. Effect of target aspect on detection range.

For example, a MIG-21 has a head-on projected area of about 40 3quare

feet and an estimated vY.sual detection range of 2.5 nautical miles. In a side

view, the projected area Increases to about 300 square feet, with an estimated

detection range of 6 nautical miles. This increase in the visual image size

enables detection to occur at a greater range. For a given aircraft, visual

ir:iage size is directly related to target aspect. Remember that target aspect

is largely determined by fighter intercept geometry. It can drastically

influence visual detection. The reverse applies to keeping the fighters

bidden. A head-on F-14 has a lower expected detection range than a side or

belly view of any of the other aircraft shown above. A head-on fighter is

much harder to see than one in planform.

6



Atmospheric conditions that decrease visibility (e.g., haze, smoke, fog,

blowing sand, etc.) will shrink the visual detection lobe ý9). There may also

be a difference between looking up through the atmosphere or down into it.

You should determine atmospheric conditions prior to engagement and make

adjustments appropriately.

Relative motion of the target (as measured by increasing or decreasing

angles off of the fighter's nose) can enable detection at a greater range. inperipheral vision, a moving target can be perceived at greater range than astatic target. Good intercept geometry can prevent the fighters from being

highlighted to the bandits by minimizing apparent motion. Abrupt maneuveringof your oircraft can give the enemy a detection advantage even though the

angular position of the two ai?:craft remains relatively stable.

contrast of the target is one of the prime determinants of detection.

Contrast is the ratio of how bright (or dark) the target is relative to the

background. A black dot stands out on a white page. Aircraft stand out

flying over an undercast.

Sun Position can have a profound influence on contrast. A sun glint off

a shiny surface offers excellent contrast and can be seen at a great

tance. In the NAMRL study, target aircraft were seen an average of 1.4

Atical miles farther away when the sun was out of the fighter 's visual

.ýeld, behind him. The sun was behind the observer in 29 of 30 engagementswhere the initial visual detection range exceeded 13 nautical miles. The

important point is that itrercept geometry that considers the position of

tbe sun can put the bandits in a high contrast field by giving the fighters•°kound to highli1ht them against. Having the sun behind you also

reduces glare and increases the possibility of a long-range sun glint tally

ho.

Clutter refers to anything but a uniform background on which to search.Clutter imposes multiple distracters in the visual field and will reduce

detection capability (10). Clutter is always present when looking down over

land. This is especially true fo r rough or mountainous terrain. Clutter

could also be imposed by a choppy cloud layer or rough seas. In most cases,

detection ranges wi l be decreased.

Aircraft exhaust smoke can aid detection. Sroke provides a relatively

large visual target usually contrasted against a blue sky or cloud undercast,

A low-angle view of any smoke trail can yield pointing information that maxi-

mizes the chance of aircraft detection. In the NAMRL study mentioned above,

visual detectiun of aircraft making smoke occurred an average of 2 nautical

miles farther away than aircraft that did no t smoke. Aircraft smoke has

received much attention over the last several years with a resultant effort to

reduce the smoke content in fighter motors. Pilots of F-4 aircraft used toengage the afterburner within 10 nautical miles of intercept, virtuallyeliminating the visible smoke content of their exhaust (which was considerable

when they used military thrust). Pilots of F-14 aircraft have also been using

this technique because of the smoke prcduced by their detuned TF-30 engines.

A caveat to remember when considering this technique, however, is the fact

that the infrared signature of an aircraft in afterburner is considerably

greater than in military thrust. This may present a problem with the re-

emergence of IR detectors in aircraft.

7



Altitude separation between aircraft can affect detection ranges.

Generally, with a target aircraft at the same altitude and, therefore, on the

horizon, the background haze is uncluttered and providies good contrast. Beaware that the same factor applies to the fighter under observation by the

bandit.

SEARCH: USING THE SENSOR

Visual search can be categorized either as localized search or search by

exclusion. Localized search occurs when the target is known, and it can be

localized by some means. This may result from a GCI call, wingman's call, ora radar lock. Those calls direct visual search to a particular sector. The

inost localized case would be looking through the diamond/box with a radar lock

on target. When searching by exclusion, the fighters are looking fo r an

unknown threat when sector location is also unknown. It is defensive lookout.

In any environment, the fighters must be aware of all aircraft near their own.This is primarily accomplished by a diligent and systematic visual search, one

that is well integrated into tactics.

Integrating Fixations

Visual search is a series of directed fixations. Each fixation has aparticular probability of detection associated with it. The more fixations ina given sector, the greater the probability of detecting a target if present.

Each individual fixation requires approximately 275 msec, which limits the

total number of fixations. By understanding these concepts, the rules of

visual search can be developed. Plotting the visual lobe for three successive

fixations would yield a search sequence, as in Fig. 4. The chance of placing

the central vision of the eyes directly on a distant bandit is quite remote

unless aided by a radar lock or UHF call. This is because the small area of

central vision, less than 2 degrees, must be moved over a much larger field In

a relatively short time (11). When searching fo r an aircraft at a closer

range (inside of 2 nautical miles), fewer fixations are required because of

the enhanced probability of detecting a bandit in peripheral vision. Visualscan can be made more time manageable by widely spaced fixations but at the

cost of decreasing the probability of detecting a distant target.

Rules of Visual Search

A large volume of sky will need to be scanned quickly. Basic visual

search is a defensive lookout, so all quadrants must be vi3wed. Other work-

load requirements will limit the time to scan.

Given a limited amount of time and a large area to search, fixations

should be widely spaced to ensure adequate coverage. Do no t expect to detect

an unknown, pop-up target at your visual acuity limits. If your fixations are

widely spaced, you will still pick up the target, bu t it will be relativelyclose--probably 1 to 2 nautical miles.

The more time spent 6earching a sector, the more likely you will be to

pick up a long-range tally if one exists in that sector. This is the case for

a known, localized aircraft. The fighter will be constrained by the size of

the detection lobe and the closure rate between aircraft. With a high rate of

closure, time to Fearch is reduced, thus decreasing detection ranges. The

8



timz spcat in'tensely searching one sector comes at the expense of others, and

this mnst be considered in the overall tactics.

900 800

K>~7OZ~600

500

400

• 100

1 2 3 4 5 6 7 -RANGE NM-.--

Figure 4. The visual detection lobe during three successive

fixations.

Secror Search

The key to visual search i3 to be systematic. This will no t onlyensure complete coverage, but it will. also enable the visual scan pattern

to become a habit. Dividing the total search area around the aircraft into

sectors gives the following search plan (Fig. 5).



1 2

A~-• , \ 450

................... ................. _ _ _ _ _ _ _

LOWER LIMIT OF

WINGS LEVEL

VISIBILUTY

BC 3 4

VERTICAL SECTORS HORIZONTAL SECTORS

Figure 5. Visual search septors.

The horizontal sectors are shown divided into 90-degree segments.

Depending on the aircraft, these segments could more easily be defined along

an aircraft structure, such as a wing line. The vertical extent is from 45

degrees above the horizon to the lower )imit of wing-level cockpit visibility.

Again, a cockpit indication would be very useful fo r the upper limit if

aircraft structure permits. The two aft sectors check high six. Low six ischecked in the two lower vertical sectors. A graphic display of a horizontal

search sector is shown in Fig. 6.

The vertical sectors are divided into two groups: the upper and the

lower. Searching the upper sector requires considerable twisting around. It

is scanned from 45 degrees high in front of the nose to 45 degrees high above

the tail. The lower sector requires a wing drop into the sector to be scan-

ned. The aft extent of search needs to include deep six. An upper vertical

search sector is shown in Fig. 7.



HORIZON---

AFT EXTENT OF SECTOR'/•

LOWER LIMIT F

VISIBI1IF. • • • d i

WINGS LEVEL\ ,•,

LOWER LIMIT OF HORIZONVISIBILITY OVER THE

NOSE OF AIRCRAFT

Figure 6. A horizontal search sector.

Figure 7. Upper vertical search sector.

The most important variable a fighter must consider is how much time to

devote to each sector. As a baseline, consider a 5-second search in eacharea, which will allow approximately 15 widely spaced fixations per sector.

This needs to be planned around the expected threat. With a rear quarter

threat, scan should be concentrated in the rear hemisphere, or if a turn is

anticipated, scan should be localized around the projected rear hemisphere. Asurface-to-air threat suggests that the lower hemisphere will need to be

emphasized. The problem becomes more difficult with a forward quarter threat.

With the high rate of closure of head-on missiles, the forward sectors will

need the emphasis. An incoming forward quarter missile allows the least

11



amount of time to react. A comprehensive study of the ability to detect and

respond to these weapons is being conducted by the NAMRL and the NFWS.

Sector Rest ongis_ iie

A fighter flying alone will have his visual scan spread very thinly

around the sky. If, however, more eyes are available, scan responsibilities

should be assigned within the cockpit and within the section. This should bea regularly briefed item. With a given volume of sky to search, two sits of

eyes can place twice the number of fixations around that volume, thus increas-

ing the probability of detection considerably. Because of aircrew workload,

this splitting of responsibilities is very important to the overall search

tactics, especially during an intercept. In two-seater aircraft, horizontal

scan responsibilities can be split fore and aft. The radar intercept officer

(RIO) could be assigned the upper vertical sector while the ilot searches thetw o lower sectors.

In the section, horizontal responsibilities can be split by assigning the

pilot to the two forward sectors and the aft sector in the direction of his

wingman. Given the increased workload of directing the intercept, the RIO

would have the outside six sector. Again, the RIO would have the upper

vertical sectors and the pilot the lower sectors. Suggested horizontal sector

assignments are shown in Fig. 8.

51GTE I

/'/

00, 0 S FIGHTER 1

FIGHTER 2

Figure 8. Pi lot of Fighter 1 sector scan responsibilities.

12



Individual Scan Patterns

Research findings in visual search point to the importance of visual cues

that provide a reference framework fo r systematic search. Suggested scan

patterns are shown in Fig. 9. They allow complete coverage of the different

sectors while providing important reference points. These are just sugges-

tions; further research is needed to determine the most effective search

techniques. Regardless, each crew member should develop a scan pattern that

assures timely but complete coverage of the assigned sector.

INDIVIDUAL FIXATIONS

", ~EYE MOVEMENT

t4EAD MOVEMENT , i

..............................

Figure 9. Visual scan patternis for horizontal sectors.

Horizontal Sectors. To scan the horizontal sectors, start scanning for-

ward above the horizon and work aft. Then, scan below the horizon workingforward. Use the peripheral view of the horizon and the head position as

orientation cues. Remember that scan goes from one fixation point to the

next. Although moved quickly, the eyes will stop momentarily to perceive any

target at each location. Plan the number of fixations and their spacing

within the time allotted ;o search in this area. Figure 9 shows a representa-

tive view of the right hjrizontal sector. The search pattern is projected

onto the scan field.

Vertical Sectors. The task becomes most difficult fo r the vertical

sectors. More than likely, the upper sector will be a uniform field without

any visual cues, such as the horizon, to help se t the pattern. The best guide

will be your sense of head position. With this in mind, work fixations in the

same line as head movements. This will ensure that the sector is uniformly

scanned. Setting focus at the beginning of search will also be v.ery impor-

tant. A sample scan pattern fo r the upper vertical field is shown in Fig.10,

For the two lower sectors, the problem will be ground clutter. This clutter

will likely decrease detection ranges unless more time is devoted to search.

In essence, think of each sector asa package to be scanned to

completion. As workload dictates, each sector is viewed in sequence. Even ifyou cani'.ot devote a full 5-second search, at least include a few fixations in

each critical sector.

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INDIVIDUAL FIXATIONS(In line with head mvement.)

V HEAD MOVEMENT

Figure 10. Scan pattern fo r upper vertical field.

SUMMARY

Visual search and detection is a complex procedure. It requires con-

tinuous airciew participation, and yet it must occur in the high-workload

environment of aerial combat. A wise fighter will carefully integrate avisual search strategy into his game plan until it becomes a habit before

engaging in aerial combat.

Visual search is a series of discrete fixations, not just rapid eye

movements. Remember to set focus at infinity beforehand. To ensure adequate

coverage in a limited amount of time, widely space each fixation. Carefully

plan the sectors around the aircraft. Se t responsibilities fo r them. Be

systematic in your search. Do not neglect sectors that are difficult to view.

To conclude with some important thoughts:

Train to perform visual search the way you intend to search in com-

bat. Vision greatly affects situational awareness in any environment.

Always strive fo r total awareness of the space around the aircraft.

It will pay big dividends in your career as fighter/strike aircrew. Totalawareness is primarily accomplished by visual search. Regardless of present

or future technological advances, the iinportance of visual search has not

changed since the first days of air combat.

Fleet inputs are needed regarding optimal search and training tech-niques. As a community, we must exploit this most important sensor. Un-

tortunately, very little training in visual search is currently available.

Even less effort has gone into the visual aspects of tactical development.

These shortcomings should be corrected.

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REFERENCES

1. Hamilton, P.V. and Morris, A., Effects of the Neutral Density Visor onthe Visual Acuity of Navy Fighter Pilots, NAMRL-1325, Naval Aerospace

Medical Research Laboratory, Pensacola, FL , December 1986.

2. Latour, P.L., "Visual Threshold During Eye Movements." Vision Research,

Vol. 2, p. 261, 1962.

3. Moffitt, K., "Evaluation of the Fixation Duration in Visual Search."

Perception and Psychophysics, Vol. 27, No. 4, pp. 370-372, 1980.

4. Whiteside, T.S., "Acco1inmodation of the Human Eye in a Bright and Empty

Visual Field." Journal of Physiology, Vol. 118, p. 65, 1952.

5. Whiteside, T.S., Vision in an Empty Visual Field: Rate of Relaxation of

Accommodation, Flying Personnel Research Committee, Document 897,

September 1954.

6 Erickson, R.A., "Relation Between Visual Search Time and Peripheral Visual

Acuity." Human Factors, Vol. 6, No. 2, pp. 165-177, April 1964

7. Overington, I., Vision and Acquisition, Pentech Press, London, 1976,

8. Hamilton, P.V. and Monaco, W. A., "Improving Air-to-Air Target Detection,"

Wings of Gold, pp. 46-48, Winter 1986.

9. Middleton, W.E.K., Vision Through the Atmosphere, University of Toronto

Press, Toronto 1952.

10. Baker, C.A., "Target Recognition on Complex Displays." Human Factors,

Vol. 2, No. 51, 1960.

11. Krendel, E.S. and Wodinsky, J., "Visual Search in Unstructured Fields."

In A. Morris and E.P. Home Visual Search Techniques, NAS-NRC

Committee, Washington, DC , pp. 151-169, 1960.

12 . Costanza, E.B., Stacey, S.R., and Snyder, H.L., Air-to-Air Target Acqui-

sition: Factors and Means of Improvement, SAM-TR-80-9, USAF School

of Aerospace Medicine, Brooks Air Force Base, TX, March 1980.

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eN

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Visual Search in Air Combat

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